1. Field of the Invention
This invention relates to an ink jet recording apparatus provided with cap means for covering the fore end of a recording head for discharging ink or suction recovering means for effecting suction recovery of the recording head.
2. Description of the Prior Art
An ink jet printer provided with suction recovering means and a recording head is shown in FIG. 1 of the accompanying drawings.
In FIG. 1, reference numerals 1 and 2 designate main tanks in which ink bags 3 are contained, respectively.
The ink bags 3 in the main tanks 1 and 2 are connected through supply tubes 4 to a sub-tank 5 mounted on a carriage.
A thin supply tube 6 is contained in the subtank 5 which is a recording head and one end thereof is connected to a nozzle 7. The other end of the supply tube 6 is immersed in the ink 8 within the sub-tank 5.
Reference numeral 9 denotes a pump which is suction means. This pump 9 is provided with a piston 10 to which an operating lever 11 is connected.
The pump 9 and the sub-tank 5 are connected together by suction tubes 12, and the pump 9 and a cap 13 for sucking ink are connected together through nozzle tubes 14.
Although not shown, the nozzle 7 is provided with a cylindrical piezo element (a piezo-electric element), and a voltage is applied to this piezo element in accordance with a printing command to compress a glass tube constituting the nozzle, thereby causing ink to be discharged and effecting printing.
Designated by 15 is a return tube which performs the function of returning the drain ink from the pump 9 to a return ink chamber 16 on the main tank 1 side.
Now, describing the positional relation between the suction tubes 12 and the nozzle tubes 14, the suction tubes 12 lie at a higher position and the nozzle tubes 14 lie at a lower position.
Accordingly, when the operating lever 11 is depressed to render the upper side of the piston 10 of the pump 9 into negative pressure, negative pressure is first supplied to the suction tube 12 and at this time, the nozzle tubes 14 are closed.
Thus, at the first stage, the interior of the sub-tank 5 is reduced in pressure and ink is sucked from the main, tanks 1 and 2 into the sub-tank 5.
When the piston 10 is being further depressed, the ink in the nozzle 7 may be sucked through the cap 13.
When ink enters the sub-tank and ink enters the suction tubes 12 by the operation of the pump 9, the resistance on the suction tubes 12 side becomes higher and thereafter, ink is sucked chiefly from the nozzle side.
As a result, bubbles in the nozzle can be eliminated and ink discharge recovery can be accomplished.
On the other hand, when ink is sucked from the suction tubes 12 and the nozzle tubes 14 by the suction of the pump, the interior of the sub-tank 5 is reduced in pressure. Accordingly, if the cap 13 is removed during the time until the interior of the sub-tank restores its original pressure after the suction, the air is sucked in through the nozzle 7 because the internal pressure of the sub-tank 5 has not yet reached its original level, and air is sucked into the nozzle causes non-discharge.
Accordingly, it is necessary to refrain from releasing the cap until this internal pressure is restored to its original level by the supply of ink from the main tank.
If the operator releases the cap neglecting this, an ink non-discharge condition will be caused to occur by the releasing of the cap in spite of the discharge recovering operation having been effected.